Rare-earth-silicon alloys or these alloys further comprising iron are used in the iron and steel industry for deoxidation, desulfurization, sulfide shape control and grain refinement, thereby producing improved properties in the products. Additionally, the rare-earth metal ore can be used in such additions as described in U.S. Pat. No. 3,065,070.
The preparation of rare-earth metal alloys is described in U.S. Pat. Nos. 3,250,609, 3,537,844, 2,926,080, 3,264,093 and 3,256,087, as well as in German Pat. Nos. 1,800,701 and 1,274,801.
A more recent description of the rare-earth metal silicide alloys is found in U.S. Pat. No. 4,018,597. The method described therein is a carbothermic reducing reaction between a rare-earth metal compound, silica and iron at temperatures in excess of about 3500.degree. F. (at least about 1926.degree. C.). However, the rare-earth metal recovery, as in other commerical smelting operations, may be less than 60%, and the rare-earth content of the product may only be about 30%.
Attempts to utilize silicon or ferrosilicon as the reductant were not totally successful since alloy products were obtained having 36% and 33% by weight rare-earth, respectively. Thus, these, as well as prior art methods, indicated that existing technology could not easily provide for the production of rare-earth-silicon alloys having high rare-earth contents, nor could the processes result in satisfactorily high net recoveries of the rare-earth values charged, the remainder being lost in the slag produced.
It is therefore an object of the present invention to provide a process for the production of a rare-earth-silicon alloy, which may additionally contain iron and other ingredients, which has a high rare-earth metal content.
An additional object of the present invention is a process for the production of a rare-earth-silicon alloy which is efficient to the extent of incorporating a large percentage of the charged rare-earth value into the alloy product.
A further object of the present invention is a process for the production of a rare-earth-silicon alloy which utilizes relatively low reaction temperatures and is readily adaptable to various reactors.
A still further object of the present invention is a rare-earth-silicon alloy which has a minor amount of aluminum, thereby increasing its value as a steel additive, and a high percentage of rare-earth metal.